Zoom lens system, lens barrel, imaging device and camera

ABSTRACT

A zoom lens system comprising a plurality of lens units each composed of at least one lens element, wherein an interval between at least any two lens units is changed so that an optical image is formed with a continuously variable magnification, any one of the lens units, any one of the lens elements, or a plurality of adjacent lens elements that constitute one lens unit move in a direction perpendicular to an optical axis, the zoom lens system comprises a first lens unit having positive power, a second lens unit that includes a lens element having a reflecting surface and has negative power and subsequent lens units including at least one lens unit having positive power, and the condition (1): 1.50&lt;M 1 /f W &lt;3.00 (M 1  is an amount of optical axial movement of the first lens unit, f W  is a focal length of the entire zoom lens system at a wide-angle limit) is satisfied.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on application No. 2006-27369 filed in Japanon Feb. 3, 2006, the content of which is hereby incorporated byreference.

BACKGROUND

1. Technical Field

The present invention relates to a zoom lens system, a lens barrel, animaging device and a camera. In particular, the present inventionrelates to: a zoom lens system that is used suitably in a small andhigh-image quality camera such as a digital still camera or a digitalvideo camera, and that has a large variable magnification ratio and ahigh resolution as well as a blur compensation function of opticallycompensating blur caused in an image by hand blur, vibration or thelike; a lens barrel that holds this zoom lens system and has a shortoverall length at the time of accommodation as well as a low overallheight; an imaging device including this lens barrel; and a thin andcompact camera employing this imaging device.

2. Description of the Background Art

With recent progress in the development of solid-state image sensorssuch as a CCD (Charge Coupled Device) and a CMOS (ComplementaryMetal-Oxide Semiconductor) having a high pixel, digital still camerasand digital video cameras are rapidly spreading that employ an imagingdevice including an imaging optical system of high optical performancecorresponding to the above solid-state image sensors of a high pixel.

Among these, especially in digital still cameras, thin constructionshave recently been proposed in order to achieve satisfactoryaccommodation property or portability to which the highest priority isimparted. As possible means for realizing such thin digital stillcameras, a large number of zoom lens systems have been proposed thatbend a light beam by 90°.

For example, Japanese Laid-Open Patent Publication No. 2004-004533 andNo. 2003-202500 disclose a construction in which in an imaging deviceprovided with a zoom lens system, a right-angle prism provided with aninternal reflecting surface for bending a light beam by 90° is arrangedinside a lens unit located on the most object side. In the imagingdevice disclosed in Japanese Laid-Open Patent Publication No.2004-004533 and No. 2003-202500, since the object light is bent in aplane perpendicular to the optical axis of the incident lens unit, thethickness of the imaging device is determined by the right-angle prismand the lens elements located on the object side relative to theright-angle prism. This reduces the thickness.

Further, Japanese Laid-Open Patent Publication No. 2004-102089 disclosesa construction in which in an imaging device provided with a zoom lenssystem composed of four units having a construction of positive,negative, positive and positive, a right-angle prism provided with aninternal reflecting surface for bending a light beam by 90° is arrangedinside a second lens unit having negative optical power. In the imagingdevice described in Japanese Laid-Open Patent Publication No.2004-102089, the right-angle prism can be arranged inside the lens unitlocated on the image side relative to the first lens unit havingpositive optical power. This allows the right-angle prism to beconstructed compactly.

Further, Japanese Laid-Open Patent Publication No. 2004-219930 disclosesa blur compensation function installed camera provided with a bendingoptical system. The camera described in Japanese Laid-Open PatentPublication No. 2004-219930 is supported in a manner freely swingableabout approximately one point of a bending member so that blurcompensation is achieved without disturbing of thickness reduction.

Nevertheless, in the zoom lens system disclosed in Japanese Laid-OpenPatent Publication No. 2004-004533, although a compact imaging devicecan be provided, the variable magnification ratio is as small asapproximately 3. Further, the optical performance is insufficient in theperiphery part and hence has caused a problem that blur compensationcannot be achieved.

Further, in the zoom lens system disclosed in Japanese Laid-Open PatentPublication No. 2003-202500 and No. 2004-102089, thickness reduction ofthe imaging device is restricted from their intrinsic construction.Further, optical performance is insufficient in the periphery part, andhence the zoom lens system is not suitable for blur compensation.

The blur compensation function installed camera disclosed in JapaneseLaid-Open Patent Publication No. 2004-219930 is provided with means foradjusting the decentration of the bending member. Nevertheless, sincethe lens system itself is not described in sufficient detail, the blurcompensation function is expected to be insufficient.

SUMMARY

An object of the present invention is to provide: a zoom lens systemthat, in addition to a large variable magnification ratio and a highresolution, has a blur compensation function of optically compensatingblur caused in an image by hand blur, vibration or the like; a lensbarrel that holds this zoom lens system and has a short overall lengthat the time of accommodation as well as a low overall height; an imagingdevice including this lens barrel; and a thin and compact cameraemploying this imaging device.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed: azoom lens system comprising a plurality of lens units each composed ofat least one lens element, wherein an interval between at least any twolens units among the lens units is changed so that an optical image ofan object is formed with a continuously variable magnification, any oneof the lens units, any one of the lens elements, or alternatively aplurality of adjacent lens elements that constitute one lens unit movein a direction perpendicular to an optical axis, the zoom lens system,in order from the object side to the image side, comprises: a first lensunit having positive optical power; a second lens unit that includes alens element having a reflecting surface for bending a light beam froman object and that has negative optical power; and subsequent lens unitsincluding at least one lens unit having positive optical power, and thefollowing condition (1) is satisfied:1.50<M ₁ /f _(W)<3.00   (1)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from a wide-angle limit to a telephoto limit,

f_(W) is a focal length of the entire zoom lens system at a wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at a telephotolimit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed: alens barrel for holding an imaging optical system that forms an opticalimage of an object, wherein the imaging optical system is a zoom lenssystem comprising a plurality of lens units each composed of at leastone lens element, in which an interval between at least any two lensunits among the lens units is changed so that an optical image of anobject is formed with a continuously variable magnification, any one ofthe lens units, any one of the lens elements, or alternatively aplurality of adjacent lens elements that constitute one lens unit movein a direction perpendicular to an optical axis, the zoom lens system,in order from the object side to the image side, comprises: a first lensunit having positive optical power; a second lens unit that includes alens element having a reflecting surface for bending a light beam froman object and that has negative optical power; and subsequent lens unitsincluding at least one lens unit having positive optical power, and thefollowing condition (1) is satisfied:1.50<M ₁ /f _(W)<3.00   (1)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

f_(W) is a focal length of the entire zoom lens system at a wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at a telephotolimit, and wherein in an imaging state, the first lens unit is held in amanner movable in a direction of the light beam from the object, and inan accommodated state, the lens element having a reflecting surfaceescapes to an escape position different from a position located in theimaging state.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed: animaging device capable of outputting an optical image of an object as anelectric image signal, comprising an imaging optical system that formsthe optical image of the object, and an image sensor that converts theoptical image formed by the imaging optical system into the electricimage signal, wherein the imaging optical system is a zoom lens systemcomprising a plurality of lens units each composed of at least one lenselement, in which an interval between at least any two lens units amongthe lens units is changed so that an optical image of an object isformed with a continuously variable magnification, any one of the lensunits, any one of the lens elements, or alternatively a plurality ofadjacent lens elements that constitute one lens unit move in a directionperpendicular to an optical axis, the zoom lens system, in order fromthe object side to the image side, comprises: a first lens unit havingpositive optical power; a second lens unit that includes a lens elementhaving a reflecting surface for bending a light beam from an object andthat has negative optical power; and subsequent lens units including atleast one lens unit having positive optical power, and the followingcondition (1) is satisfied:1.50<M ₁ /f _(W)<3.00   (1)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

f_(W) is a focal length of the entire zoom lens system at a wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at a telephotolimit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed: acamera for converting an optical image of an object into an electricimage signal and then performing at least one of displaying and storingof the converted image signal, comprising an imaging device including animaging optical system that forms the optical image of the object and animage sensor that converts the optical image formed by the imagingoptical system into the electric image signal, wherein the imagingoptical system is a zoom lens system comprising a plurality of lensunits each composed of at least one lens element, in which an intervalbetween at least any two lens units among the lens units is changed sothat an optical image of an object is formed with a continuouslyvariable magnification, any one of the lens units, any one of the lenselements, or alternatively a plurality of adjacent lens elements thatconstitute one lens unit move in a direction perpendicular to an opticalaxis, the zoom lens system, in order from the object side to the imageside, comprises: a first lens unit having positive optical power; asecond lens unit that includes a lens element having a reflectingsurface for bending a light beam from an object and that has negativeoptical power; and subsequent lens units including at least one lensunit having positive optical power, and the following condition (1) issatisfied:1.50<M ₁ /f _(W)<3.00   (1)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

f_(W) is a focal length of the entire zoom lens system at a wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at a telephotolimit.

The present invention provides a zoom lens system that, in addition to alarge variable magnification ratio and a high resolution, has a blurcompensation function of optically compensating blur caused in an imageby hand blur, vibration or the like. Further, the present inventionprovides a lens barrel that holds this zoom lens system and that has ashort overall length at the time of accommodation as well as a lowoverall height. Furthermore, the present invention provides an imagingdevice including this lens barrel and a thin and compact cameraemploying this imaging device.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1A is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 1;

FIG. 1B is a transparent perspective view showing an outlineconfiguration in an accommodated state of a camera employing an imagingdevice according to Embodiment 1;

FIG. 2A is a lens arrangement diagram showing an arrangement of animaging optical system in an imaging state at a wide-angle limit inEmbodiment 1;

FIG. 2B is a lens arrangement diagram showing an arrangement of animaging optical system in an accommodated state in Embodiment 1;

FIGS. 3A to 3C are sectional views showing arrangements of a lens barrelof an imaging device according to Embodiment 1 respectively in animaging state at a telephoto limit, in an imaging state at a wide-anglelimit and in an accommodated state;

FIG. 4A is a transparent perspective view showing an outlineconfiguration of an imaging state of a camera employing an imagingdevice according to a modification of Embodiment 1;

FIG. 4B is a transparent perspective view showing an outlineconfiguration of an accommodated state of a camera employing an imagingdevice according to a modification of Embodiment 1;

FIG. 5A is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 2;

FIG. 5B is a transparent perspective view showing an outlineconfiguration in an accommodated state of a camera employing an imagingdevice according to Embodiment 2;

FIG. 6A is a lens arrangement diagram showing an arrangement of animaging optical system in an imaging state at a wide-angle limit inEmbodiment 2;

FIG. 6B is a lens arrangement diagram showing an arrangement of animaging optical system in an accommodated state in Embodiment 2;

FIGS. 7A to 7C are sectional views showing arrangements of a lens barrelof an imaging device according to Embodiment 2 respectively in animaging state at a telephoto limit, in an imaging state at a wide-anglelimit and in an accommodated state;

FIG. 8A is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 3;

FIG. 8B is a transparent perspective view showing an outlineconfiguration in an accommodated state of a camera employing an imagingdevice according to Embodiment 3;

FIG. 9A is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 4;

FIG. 9B is a transparent perspective view showing an outlineconfiguration in an accommodated state of a camera employing an imagingdevice according to Embodiment 4;

FIG. 10A is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 5;

FIG. 10B is a transparent perspective view showing an outlineconfiguration in an accommodated state of a camera employing an imagingdevice according to Embodiment 5;

FIGS. 11A to 11C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 6 (Example 1) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 12A to 12I are longitudinal aberration diagrams of a zoom lenssystem according to Example 1 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 13A to 13F are lateral aberration diagrams of a zoom lens systemaccording to Example 1 at a telephoto limit;

FIGS. 14A to 14C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 7 (Example 2) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 15A to 15I are longitudinal aberration diagrams of a zoom lenssystem according to Example 2 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 16A to 16F are lateral aberration diagrams of a zoom lens systemaccording to Example 2 at a telephoto limit;

FIGS. 17A to 17C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 8 (Example 3) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 18A to 18I are longitudinal aberration diagrams of a zoom lenssystem according to Example 3 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 19A to 19F are lateral aberration diagrams of a zoom lens systemaccording to Example 3 at a telephoto limit;

FIGS. 20A to 20C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 9 (Example 4) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 21A to 21I are longitudinal aberration diagrams of a zoom lenssystem according to Example 4 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 22A to 22F are lateral aberration diagrams of a zoom lens systemaccording to Example 4 at a telephoto limit;

FIGS. 23A to 23C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 10 (Example 5) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 24A to 24I are longitudinal aberration diagrams of a zoom lenssystem according to Example 5 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 25A to 25F are lateral aberration diagrams of a zoom lens systemaccording to Example 5 at a telephoto limit;

FIGS. 26A to 26C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 11 (Example 6) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 27A to 27I are longitudinal aberration diagrams of a zoom lenssystem according to Example 6 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit; and

FIGS. 28A to 28F are lateral aberration diagrams of a zoom lens systemaccording to Example 6 at a telephoto limit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1A is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 1. FIG. 1B is a transparent perspectiveview showing an outline configuration in the accommodated state of acamera employing the imaging device according to Embodiment 1. Here,FIGS. 1A and 1B are drawings schematically showing an imaging deviceaccording to Embodiment 1. Thus, the scale and the detailed layout candiffer from actual ones.

In FIGS. 1A and 1B, a camera employing an imaging device according toEmbodiment 1 comprises a body 1, an image sensor 2, a shutter button 3,an object side lens unit 4, a lens element 5 having a reflectingsurface, and an image side lens unit 6. Among these, the object sidelens unit 4, the lens element 5 having a reflecting surface, and theimage side lens unit 6 constitute the zoom lens system, and thereby forman optical image of an object in the light acceptance surface of theimage sensor 2. Among these, the zoom lens system is held, for example,by a lens holding barrel in a lens barrel shown in FIG. 3 describedlater, while the zoom lens system held by the lens holding barrel andthe image sensor 2 constitute an imaging device. Thus, the cameracomprises: the body 1; and the imaging device constructed from the zoomlens system and the image sensor 2.

In an imaging state shown in FIG. 1A, the image sensor 2 is an imagesensor such as a CCD or a CMOS, and generates and outputs an electricimage signal on the basis of the optical image formed in the lightacceptance surface by the zoom lens system. The shutter button 3 isarranged on the top face of the body 1, and determines the acquisitiontiming for an image signal of the image sensor 2 when operated by anoperator. The object side lens unit 4 is held inside a lens holdingbarrel which can be expanded and contracted along the direction of theoptical axis AX1. The lens element 5 is provided with a reflectingsurface for bending a light beam from an object, that is, a reflectingsurface 5 a for bending by approximately 90° the optical axis AX1 of theobject side lens unit 4 (an axial principal ray from the object), andthereby deflects the object light exiting from the object side lens unit4 toward the image side lens unit 6. The image side lens unit 6 isarranged on the optical axis AX2, and thereby transmits the object lightdeflected by the reflecting surface 5 a to the image sensor 2.

In an accommodated state shown in FIG. 1B, the object side lens unit 4is retracted and accommodated into the body 1. The lens element 5 havinga reflecting surface arranged on the image side of the object side lensunit 4 in the imaging state is escaped to the image sensor 2 side alongthe optical axis AX2, that is, on the image side of the zoom lenssystem. Further, the image side lens unit 6 is also escaped to the imagesensor 2 side along the optical axis AX2, that is, on the image side ofthe zoom lens system. As such, the zoom lens system is completelyaccommodated into the body 1.

In transition from the imaging state shown in FIG. 1A to theaccommodated state shown in FIG. 1B, the image side lens unit 6 firstmoves toward the image sensor 2 along the optical axis AX2 as indicatedby an arrow a3. Then, the lens element 5 having a reflecting surfacemoves toward the image sensor 2 along the optical axis AX2 as indicatedby an arrow a2. Finally, the lens holding barrel that holds the objectside lens unit 4 is retracted along the optical axis AX1 as indicated byan arrow a1 into a space formed by the movement of the image side lensunit 6 and the lens element 5 having a reflecting surface. As a result,the transition to the accommodated state is completed.

On the contrary, in transition from the accommodated state shown in FIG.1B to the imaging state shown in FIG. 1A, the lens holding barrel forholding the object side lens unit 4 is drawn out along the optical axisAX1 as indicated by an arrow b1. Then, the lens element 5 having areflecting surface moves along the optical axis AX2 as indicated by anarrow b2 into the space formed by the draw-out of the lens holdingbarrel for holding the object side lens unit 4. Further, the image sidelens unit 6 moves along the optical axis AX2 as indicated by an arrowb3, so that the transition to the imaging state is completed.

FIG. 2A is a lens arrangement diagram showing an arrangement of the zoomlens system in the imaging state at a wide-angle limit in Embodiment 1.FIG. 2B is a lens arrangement diagram showing an arrangement of the zoomlens system in the accommodated state in Embodiment 1. The zoom lenssystem according to Embodiment 1, in order from the object side to theimage side, comprises: a first lens unit G1 having positive opticalpower; a second lens unit G2 having negative optical power; andsubsequently a diaphragm A, a third lens unit G3, a fourth lens unit G4and a fifth lens unit G5. Further, a straight line drawn on the rightmost side in the figure indicates the position of an image surface S. Onits object side, a plane parallel plate P such as an optical low-passfilter, a face plate of the image sensor or the like is provided. Aprism L5 serving as a lens element having a reflecting surface isarranged inside the second lens unit G2.

In the zoom lens system of Embodiment 1, in the accommodated state shownin FIG. 2B, among the second lens unit G2 components, the negativemeniscus lens element L4 located on the most object side is accommodatedin a manner separated from the prism L5 serving as a lens element havinga reflecting surface and the subsequent lens elements L6 and L7. Thatis, the negative meniscus lens element L4 is held separately from theprism L5 and the subsequent lens elements L6 and L7, and hence is notfollow the escape along the optical axis AX2 performed by a lens blockconsisting of the prism L5 and the subsequent lens elements L6 and L7.Thus, the negative meniscus lens element L4 is retracted andaccommodated along the optical axis AX1 together with the first lensunit G1.

FIGS. 3A to 3C are sectional views showing arrangements of a lens barrelincluding the zoom lens system in the imaging device according toEmbodiment 1. FIG. 3A is a sectional view showing an arrangement of thelens barrel in the imaging state at a telephoto limit. FIG. 3B is asectional view showing an arrangement of the lens barrel in the imagingstate at a wide-angle limit. FIG. 3C is a sectional view showing anarrangement of the lens barrel in the accommodated state.

The lens barrel of the imaging device according to Embodiment 1comprises a main barrel 10, a first lens unit holding multi-stage barrel11, a second lens unit holding barrel 12, a third lens unit holdingbarrel 13, a fourth lens unit holding barrel 14, a fifth lens unitholding barrel 15, a guide shaft 16 a and a guide shaft 16 b.

The main barrel 10 is a body capable of accommodating the entireconstruction of the imaging device in the accommodated state. In theimaging state shown in FIGS. 3A and 3B, the second lens unit holdingbarrel 12, the third lens unit holding barrel 13, the fourth lens unitholding barrel 14, the fifth lens unit holding barrel 15, the guideshaft 16 a and the guide shaft 16 b are located in the main barrel 10.

The first lens unit holding multi-stage barrel 11 is an expandablethree-stage lens barrel. Draw-out and barrel escape along the opticalaxis AX1 are driven by a drive motor and a drive mechanism which are notshown. In the first lens unit holding multi-stage barrel 11, the firstlens unit is held in a barrel having the smallest inner diameter.Further, a barrel having the largest inner diameter is provided with aholding section 11 a for holding the negative meniscus lens element L4located on the most object side in the second lens unit.

The second lens unit holding barrel 12 holds the components located onthe image sensor side relative to the prism L5, among the second lensunit components. The third lens unit holding barrel 13 and the fourthlens unit holding barrel 14 hold the third lens unit and the fourth lensunit, respectively. The fifth lens unit holding barrel 15 holds thefifth lens unit, the plane parallel plate P and the image sensor 2.

The second lens unit holding barrel 12, the third lens unit holdingbarrel 13 and the fourth lens unit holding barrel 14 are guided on twoguide shafts 16 a and 16 b arranged in parallel to the optical axis AX2,and held in a manner movable along the optical axis AX2. Further, thesecond lens unit holding barrel 12, the third lens unit holding barrel13 and the fourth lens unit holding barrel 14 are driven along theoptical axis AX2 by a drive motor and a drive mechanism which are notshown. In each of the guide shafts 16 a and 16 b, one end is held by thefifth lens unit holding barrel 15, while the other end is held at a topend 10 a of the main barrel 10, so that the guide shafts are fixed.

As to the above construction, in the imaging state at a telephoto limitshown in FIG. 3A, in the lens barrel, the first lens unit holdingmulti-stage barrel 11 is drawn out along the optical axis AX1 to themaximum, while the interval between the first lens unit and the secondlens unit is maintained at maximum. Further, the second lens unitholding barrel 12, the third lens unit holding barrel 13, the fourthlens unit holding barrel 14, and the fifth lens unit holding barrel 15are arranged respectively at predetermined positions on the optical axisAX2 at a telephoto limit.

In transition from the imaging state at a telephoto limit shown in FIG.3A to the imaging state at a wide-angle limit shown in FIG. 3B, thefirst lens unit holding multi-stage barrel 11 is shortened along theoptical axis AX2 to the minimum length, and then stops at a positionwhere the interval between the first lens unit and the second lens unitbecomes minimum. At that time, during the shortening of the first lensunit holding multi-stage barrel 11, the lens element L4 held in theholding section 11 a of the first lens unit holding multi-stage barrel11 is fixed such that the interval with the prism L5 should not vary.Further, the third and fourth lens unit holding barrels 13 and 14 movealong the optical axis AX2 in a manner guided by the guide shafts 16 aand 16 b, and then stop respectively at predetermined positions on theoptical axis AX2 at a wide-angle limit. Here, during this time, thesecond lens unit holding barrel 12 and the fifth lens unit holdingbarrel 15 are fixed.

As shown in FIGS. 3A and 3B, in zooming from the wide-angle limit to thetelephoto limit at the time of imaging, the interval does not varybetween the lens element L4 held by the holding section 11 a of thefirst lens unit holding multi-stage barrel 11 and the prism L5 held bythe second lens unit holding barrel 12. Thus, the construction of thesecond lens unit located on the image sensor side relative to the prismL5 held by the second lens unit holding barrel 12 is fixed at apredetermined position on the optical axis AX2. That is, in zooming fromthe wide-angle limit to the telephoto limit at the time of imaging, thesecond lens unit does not move in the optical axis direction.

In transition from the imaging state at a wide-angle limit shown in FIG.3B to the accommodated state shown in FIG. 3C, the third and fourth lensunit holding barrels 13 and 14 move along the optical axis AX2 in amanner guided by the guide shafts 16 a and 16 b, and then stoprespectively at predetermined positions such as to form a space foraccommodating the second lens unit holding barrel 12. During thismovement, the fifth lens unit holding barrel 15 is fixed. Further, thesecond lens unit holding barrel 12 moves along the optical axis AX2, andthereby escape the lens elements except for the lens element L4 locatedon the most object side among the second lens unit components. Afterthat, the first lens unit holding multi-stage barrel 11 is retractedalong the optical axis AX1 with maintaining the minimum length, therebyaccommodated into the main barrel 10, and then stops.

As described above, according to the zoom lens system of Embodiment 1,in the accommodated state, the lens element having a reflecting surfacecan escape to an escape position different from the position located inthe imaging state. Thus, the air space generated in the imaging statecan be used effectively, so that a zoom lens system having a largevariable magnification ratio and a high magnification can beaccommodated in a manner compact and thin in the optical axis directionof the axial light beam from the object.

Further, the zoom lens system according to Embodiment 1 includes a lenselement having a reflecting surface for bending the light beam from theobject, that is, a reflecting surface for bending by approximately 90°the axial principal ray from the object. Thus, in the imaging state, thezoom lens system can be constructed in a manner thin in the optical axisdirection of the axial light beam from the object.

Further, the zoom lens system of Embodiment 1 includes: an object sidelens unit located on the object side relative to the lens element havinga reflecting surface; and an image side lens unit located on the imageside relative to the lens element having a reflecting surface. Thus,even a complicated zoom lens system of high magnification that has alarge amount of movement of the lens unit can be constructed in a mannercompact and thin in the optical axis direction of the axial light beamfrom the object.

Further, according to the zoom lens system of Embodiment 1, the lenselement having a reflecting surface escapes in a direction perpendicularto the not-reflected axial principal ray from the object. This permits aconstruction that the zoom lens system becomes thin in the optical axisdirection of the axial light beam from the object. In particular,according to the zoom lens system of Embodiment 1, the escape of thelens element having a reflecting surface is performed to the image sideof the zoom lens system. Thus, the air space generated in the imagingstate can be used as an accommodation space for the lens element havinga reflecting surface. This realizes a considerably compact accommodatedstate.

Further, the zoom lens system of Embodiment 1, in order from the objectside to the image side, comprises: a first lens unit having positiveoptical power; a second lens unit having negative optical power; andsubsequent lens units including at least one lens unit having positiveoptical power. Further, a lens element having a reflecting surface isarranged inside the second lens unit. Thus, the size can be reduced inthe reflecting surface. In particular, the zoom lens system can beconstructed in a manner thin in the optical axis direction of the axiallight beam from the object. Further, the size can be reduced in theprecise lens element having a reflecting surface. This reduces the costof the zoom lens system.

Further, according to the zoom lens system of Embodiment 1, the secondlens unit, in order from the object side to the image side, includes: anegative meniscus lens element whose image side surface has the moreintense optical power; a lens element having a reflecting surface; andat least one subsequent lens element. This negative meniscus lenselement reduces the incident angle at the time that the light beam fromthe object is incident on the reflecting surface.

In particular, according to the zoom lens system of Embodiment 1, in theaccommodated state, the negative meniscus lens element is separated fromthe lens element having a reflecting surface and does not escape. Thisavoids the necessity that the negative meniscus lens element which hasintense optical power and hence high decentration sensitivity is movedfrom the optical axis. Thus, in the transition from the accommodatedstate to the imaging state, restoration is achieved in a state that therelative spatial arrangement is maintained between the first lens unitand the negative meniscus lens element.

Here, in general, the zoom lens system according to Embodiment 1 isaccommodated into the lens barrel in the state shown in FIG. 3C. In thiscase, the zoom lens system can be constructed in an especially compactand thin manner in the optical axis direction of the axial light beamfrom the object. Alternatively, the accommodated state may be adoptedsuch that transition from the state of telephoto limit shown in FIG. 3Ato the state of wide-angle limit shown in FIG. 3B has been completed sothat the first lens unit holding multi-stage barrel is shortened to theminimum length and then stops at a position where the interval betweenthe first lens unit and the second lens unit becomes minimum. In thiscase, for example, the time from power start-up of the imaging device tophotographing can be shortened.

FIG. 4A is a transparent perspective view showing a diagrammaticconstruction in an imaging state of a camera employing an imaging deviceaccording to a modification of Embodiment 1. FIG. 4B is a transparentperspective view showing a diagrammatic construction in an accommodatedstate of a camera employing an imaging device according to themodification of Embodiment 1. In FIGS. 4A and 4B, the same components asEmbodiment 1 are designated by the same numerals. Then, theirdescription is omitted.

The imaging device according to the modification is different from theimaging device according to Embodiment 1 described in FIGS. 1A to 1B, 2Ato 2B and 3A to 3C in the point that the lens element 7 having areflecting surface 7 a has a cube shape. As such, the embodiment of thelens element having a reflecting surface is not limited to a specificone. That is, the lens element having a reflecting surface may be anyone of: an internal reflection mirror having a parallel plate shape; asurface reflection mirror having a parallel plate shape; and a surfacereflection prism. However, a prism having negative optical power ispreferred in particular. Further, the reflecting surface may befabricated by any one of known methods including: vapor deposition ofmetal such as aluminum; and forming of a dielectric multilayer film.Further, the reflecting surface need not have a reflectance of 100%.Thus, the reflectance may be appropriately adjusted when light forphotometry or for an optical finder system need be extracted from theobject light, or alternatively when the reflecting surface is used aspart of an optical path for projecting auto-focusing auxiliary light orthe like through itself.

Here, also for the lens barrel employed in the camera shown in FIGS. 4Aand 4B, similarly to the above case, the accommodated state may beadopted such that the transition has been completed from the state oftelephoto limit to the state of wide-angle limit so that the first lensunit holding multi-stage barrel is shortened to the minimum length andthen stops at a position where the interval between the first lens unitand the second lens unit becomes minimum.

Embodiment 2

FIG. 5A is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 2. FIG. 5B is a transparent perspectiveview showing an outline configuration in the accommodated state of acamera employing the imaging device according to Embodiment 2. In FIGS.5A and 5B, the same components as Embodiment 1 are designated by thesame numerals. Then, their description is omitted.

The imaging device according to Embodiment 2 is different from theimaging device according to Embodiment 1 in the point that the blockescaping in the accommodated state includes a lens element 5 b arrangedon the object side relative to the lens element 5 having a reflectingsurface.

In transition from the imaging state shown in FIG. 5A to theaccommodated state shown in FIG. 5B, the image side lens unit 6 firstmoves toward the image sensor 2 along the optical axis AX2 as indicatedby an arrow a3. Then, the lens element 5 having a reflecting surface andthe lens element 5 b move toward the image sensor 2 along the opticalaxis AX2 as indicated by an arrow a2. Finally, the lens holding barrelthat holds the object side lens unit 4 is retracted along the opticalaxis AX1 as indicated by an arrow a1 into a space formed by the movementof the image side lens unit 6, the lens element 5 having a reflectingsurface, and the lens element 5 b. As a result, the transition to theaccommodated state is completed.

On the contrary, in transition from the accommodated state shown in FIG.5B to the imaging state shown in FIG. 5A, the lens holding barrel forholding the object side lens unit 4 is drawn out along the optical axisAX1 as indicated by an arrow b1. The lens element 5 having a reflectingsurface and the lens element 5 b move along the optical axis AX2 asindicated by an arrow b2 into the space formed by the draw-out of thelens holding barrel for holding the object side lens unit 4. Further,the image side lens unit 6 moves along the optical axis AX2 as indicatedby an arrow b3, so that the transition to the imaging state iscompleted.

FIG. 6A is a lens arrangement diagram showing an arrangement of the zoomlens system in the imaging state at a wide-angle limit in Embodiment 2.FIG. 6B is a lens arrangement diagram showing an arrangement of the zoomlens system in the accommodated state in Embodiment 2. The zoom lenssystem according to Embodiment 2 has the same construction as the zoomlens system described in Embodiment 1. The zoom lens system, in orderfrom the object side to the image side, comprises: a first lens unit G1having positive optical power; a second lens unit G2 having negativeoptical power; and subsequently a diaphragm A, a third lens unit G3, afourth lens unit G4 and a fifth lens unit G5. Further, a straight linedrawn on the right most side in the figure indicates the position of animage surface S. On its object side, a plane parallel plate P such as anoptical low-pass filter, a face plate of the image sensor or the like isprovided. A prism L5 serving as a lens element having a reflectingsurface is arranged inside the second lens unit G2.

In the zoom lens system according to Embodiment 2, in the accommodatedstate shown in FIG. 6B, the entirety of the second lens unit G2, thatis, construction including the negative meniscus lens element L4 locatedon the most object side, the prism L5 serving as a lens element having areflecting surface and the subsequent lens elements L6 and L7, escapesintegrally.

FIGS. 7A to 7C are sectional views showing arrangements of a lens barrelincluding the zoom lens system in the imaging device according toEmbodiment 2. FIG. 7A is a sectional view showing an arrangement of thelens barrel in the imaging state at a telephoto limit. FIG. 7B is asectional view showing an arrangement of the lens barrel in the imagingstate at a wide-angle limit. FIG. 7C is a sectional view showing anarrangement of the lens barrel in the accommodated state. The lensbarrel in Embodiment 2 is different from Embodiment 1 in the point thata second lens unit holding barrel 22 holds the entirety of the secondlens unit from the lens element L4 via the prism L5 to the twosubsequent lens elements.

In Embodiment 2, in transition from the imaging state at a telephotolimit shown in FIG. 7A to the imaging state at a wide-angle limit shownin FIG. 7B, operation is performed similarly to Embodiment 1. On theother hand, in transition from the imaging state at a wide-angle limitshown in FIG. 7B to the accommodated state shown in FIG. 7C, the secondlens unit holding barrel 22 moves along the optical axis AX2, andthereby escapes the entire second lens unit. After that, a first lensunit holding multi-stage barrel 21 is retracted along the optical axisAX1 with maintaining the minimum length, thereby accommodated into themain barrel 10, and then stopped.

As shown in FIGS. 7A and 7B, in zooming from the wide-angle limit to thetelephoto limit at the time of imaging, the entirety from the lenselement L4 via the prism L5 to the two subsequent lens elements held bythe second lens unit holding barrel 22 is fixed at a predeterminedposition on the optical axis AX2. That is, in zooming from thewide-angle limit to the telephoto limit at the time of imaging, thesecond lens unit does not move in the optical axis direction.

As described above, according to the zoom lens system of Embodiment 2,in addition to the common construction described in Embodiment 1, in theaccommodated state, the entire second lens unit escapes together withthe lens element having a reflecting surface. Thus, in the transitionfrom the accommodated state to the imaging state, restoration isachieved in a state that the relative positional relation is maintainedin the second lens unit. This improves restoration accuracy.

Here, also for the lens barrel shown in FIGS. 7A to 7C, similarly to theabove case, the accommodated state may be the state of FIG. 7B where thetransition has been completed from the state of telephoto limit to thestate of wide-angle limit so that the first lens unit holdingmulti-stage barrel is shortened to the minimum length and then stops ata position where the interval between the first lens unit and the secondlens unit becomes minimum.

Embodiment 3

FIG. 8A is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 3. FIG. 8B is a transparent perspectiveview showing an outline configuration in the accommodated state of acamera employing the imaging device according to Embodiment 3. In FIGS.8A and 8B, the same components as Embodiment 1 are designated by thesame numerals. Then, their description is omitted.

The imaging device according to Embodiment 3 is different from theimaging device according to Embodiment 1 in the point that in theaccommodated state, a block escapes not in the direction of the opticalaxis AX2 of the image side lens unit 6 but in a direction perpendicularto the optical axis AX2.

In transition from the imaging state shown in FIG. 8A to theaccommodated state shown in FIG. 8B, the lens element 5 having areflecting surface first moves in a direction perpendicular to theoptical axis AX2 as indicated by an arrow a4. Then, the lens holdingbarrel for holding the object side lens unit 4 is retracted along theoptical axis AX1 as indicated by an arrow a1 into a space formed by themovement of the lens element 5 having a reflecting surface. As a result,the transition to the accommodated state is completed.

On the contrary, in transition from the accommodated state shown in FIG.8B to the imaging state shown in FIG. 8A, the lens holding barrel forholding the object side lens unit 4 is drawn out along the optical axisAX1 as indicated by an arrow b1. Then, the lens element 5 having areflecting surface moves in a direction perpendicular to the opticalaxis AX2 as indicated by an arrow b4, and enters into a space formed bythe draw-out of the lens holding barrel for holding the object side lensunit 4. As a result, the transition to the imaging state is completed.

As described above, in the zoom lens system according to Embodiment 3,in addition to the common construction described in Embodiment 1, thelens element having a reflecting surface escapes in a directionperpendicular to the optical axis AX2. Thus, the image side lens unitneed not move at the time of transition to the accommodated state. Thissimplifies the mechanism and allows the zoom lens system to beconstructed compactly in the optical axis AX2 direction.

Here, also in the lens barrel employed in the camera shown in FIGS. 8Ato 8B, similarly to the above case, the accommodated state may beadopted such that the transition has been completed from the state oftelephoto limit to the state of wide-angle limit so that the first lensunit holding multi-stage barrel is shortened to the minimum length andthen stops at a position where the interval between the first lens unitand the second lens unit becomes minimum.

Embodiment 4

FIG. 9A is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 4. FIG. 9B is a transparent perspectiveview showing an outline configuration in the accommodated state of acamera employing the imaging device according to Embodiment 4. In FIGS.9A and 9B, the same components as Embodiment 2 are designated by thesame numerals. Then, their description is omitted.

The imaging device according to Embodiment 4 is different from theimaging device according to Embodiment 2 in the point that in theaccommodated state, a block escapes not in the direction of the opticalaxis AX2 of the image side lens unit 6 but in a direction perpendicularto the optical axis AX2.

In transition from the imaging state shown in FIG. 9A to theaccommodated state shown in FIG. 9B, the lens element 5 having areflecting surface and the lens element 5 b first move in a directionperpendicular to the optical axis AX2 as indicated by an arrow a4. Then,the lens holding barrel that holds the object side lens unit 4 isretracted along the optical axis AX1 as indicated by an arrow a1 into aspace formed by the movement of the lens element 5 having a reflectingsurface and the lens element 5 b. As a result, the transition to theaccommodated state is completed.

On the contrary, in transition from the accommodated state shown in FIG.9B to the imaging state shown in FIG. 9A, the lens holding barrel forholding the object side lens unit 4 is drawn out along the optical axisAX1 as indicated by an arrow b1. Then, the lens element 5 having areflecting surface and the lens element 5 b move in a directionperpendicular to the optical axis AX2 as indicated by an arrow b4, andenter into a space formed by the draw-out of the lens holding barrelthat holds the object side lens unit 4. As a result, the transition tothe imaging state is completed.

As described above, in the lens barrel according to Embodiment 4, inaddition to the common construction described in Embodiment 2, the lenselement having a reflecting surface escapes in a direction perpendicularto the optical axis AX2. Thus, the image side lens unit need not move atthe time of transition to the accommodated state. This simplifies themechanism and allows the zoom lens system to be constructed compactly inthe optical axis AX2 direction.

Here, also in the lens barrel employed in the camera shown in FIGS. 9Ato 9B, similarly to the above case, the accommodated state may beadopted such that the transition has been completed from the state oftelephoto limit to the state of wide-angle limit so that the first lensunit holding multi-stage barrel is shortened to the minimum length andthen stops at a position where the interval between the first lens unitand the second lens unit becomes minimum.

Embodiment 5

FIG. 10A is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 5. FIG. 10B is a transparent perspectiveview showing an outline configuration in the accommodated state of acamera employing the imaging device according to Embodiment 5. In FIGS.10A and 10B, the same components as Embodiment 1 are designated by thesame numerals. Then, their description is omitted.

The imaging device according to Embodiment 5 is the same as the imagingdevice according to Embodiments 1 to 4. However, the arrangementdirection layout of the optical axis AX2 is different at the time ofarranging in the camera. That is, in the camera employing the imagingdevice according to Embodiments 1 to 4, the optical axis AX2 has beenarranged perpendicularly to the stroke direction of the shutter button3, so that the imaging device has been arranged horizontally. Incontrast, in the camera employing the imaging device according toEmbodiment 5, the optical axis AX2 is arranged in parallel to the strokedirection of the shutter button 3, so that the imaging device isarranged vertically.

As such, in the imaging device according to Embodiment 5, arrangementflexibility is increased when the imaging device is applied to thecamera, and so is the flexibility in designing of a camera.

Here, also in the lens barrel employed in the camera shown in FIGS. 10Ato 10B, similarly to the above case, the accommodated state may beadopted such that the transition has been completed from the state oftelephoto limit to the state of wide-angle limit so that the first lensunit holding multi-stage barrel is shortened to the minimum length andthen stops at a position where the interval between the first lens unitand the second lens unit becomes minimum.

Embodiments 6 to 11

The zoom lens system applicable to the imaging device of Embodiments 1to 5 is described below in further detail with reference to thedrawings. FIGS. 11A to 11C are lens arrangement diagrams of a zoom lenssystem according to Embodiment 6. FIGS. 14A to 14C are lens arrangementdiagrams of a zoom lens system according to Embodiment 7. FIGS. 17A to17C are lens arrangement diagrams of a zoom lens system according toEmbodiment 8. FIGS. 20A to 20C are lens arrangement diagrams of a zoomlens system according to Embodiment 9. FIGS. 23A to 23C are lensarrangement diagrams of a zoom lens system according to Embodiment 10.FIGS. 26A to 26C are lens arrangement diagrams of a zoom lens systemaccording to Embodiment 11. FIGS. 11A, 14A, 17A, 20A, 23A and 26A showthe lens construction at a wide-angle limit (the shortest focal lengthcondition: focal length f_(W)). FIGS. 11B, 14B, 17B, 20B, 23B and 26Bshow the lens construction at the middle position (the middle focallength condition: focal length f_(M)=√(f_(W)*f_(T)) ). FIGS. 11C, 14C,17C, 20C, 23C and 26C show the lens construction at a telephoto limit(the longest focal length condition: focal length f_(T)).

Each zoom lens system according to Embodiments 6 to 11, in order fromthe object side to the image side, comprises: a first lens unit G1having positive optical power; a second lens unit G2 having negativeoptical power; a diaphragm A; a third lens unit G3 having positiveoptical power; and a fourth lens unit G4 having positive optical power.Here, each of a prism which is a third lens element L3 in Embodiments 6and 9 or a fourth lens element L4 in Embodiments 7, 8 and 10, and amirror in Embodiment 11, corresponds to the lens element having areflecting surface. In the description, the position of the reflectingsurface is omitted. Further, in each of FIGS. 11A to 11C, 14A to 14C,17A to 17C, 20A to 20C, 23A to 23C and 26A to 26C, a straight line drawnon the rightmost side indicates the position of an image surface S. Onits object side, a plane parallel plate P such as an optical low-passfilter, a face plate of an image sensor or the like is provided. In thezoom lens system according to Embodiments 6 to 11, these lens units arearranged in a desired optical power construction, so that size reductionis achieved in the entire lens system in a state that high magnificationvariation ratio is achieved and that high optical performance issatisfied.

As shown in FIGS. 11A to 11C, in the zoom lens system according toEmbodiment 6, the first lens unit G1 comprises solely a positivemeniscus first lens element L1 with the convex surface facing the objectside.

In the zoom lens system according to Embodiment 6, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus second lens element L2 with the convex surface facingthe object side; a lens element L3 having plane incident and exitsurfaces and a reflecting surface; a bi-concave fourth lens element L4;and a bi-convex fifth lens element L5.

Further, in the zoom lens system according to Embodiment 6, the thirdlens unit G3, in order from the object side to the image side,comprises: a positive meniscus sixth lens element L6 with the convexsurface facing the object side; a bi-convex seventh lens element L7; anda bi-concave eighth lens element L8. Among these, the seventh lenselement L7 and the eighth lens element L8 are cemented with each other.

In the zoom lens system according to Embodiment 6, the fourth lens unitG4, in order from the object side to the image side, comprises: apositive meniscus ninth lens element L9 with the convex surface facingthe object side; and a positive meniscus tenth lens element L10 with theconvex surface facing the object side. The ninth lens element L9 and thetenth lens element L10 are cemented with each other.

In the zoom lens system according to Embodiment 6, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As shown in FIGS. 14A to 14C, in the zoom lens system according toEmbodiment 7, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; and a positive meniscussecond lens element L2 with the convex surface facing the object side.The first lens element L1 and the second lens element L2 are cementedwith each other.

In the zoom lens system according to Embodiment 7, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus third lens element L3 with the convex surface facingthe object side; a lens element L4 having plane incident and exitsurfaces and a reflecting surface; a bi-concave fifth lens element L5;and a bi-convex sixth lens element L6.

In the zoom lens system according to Embodiment 7, the third lens unitG3, in order from the object side to the image side, comprises: apositive meniscus seventh lens element L7 with the convex surface facingthe object side; and a negative meniscus eighth lens element L8 with theconvex surface facing the object side.

Furthermore, in the zoom lens system according to Embodiment 7, thefourth lens unit G4 comprises solely a positive meniscus ninth lenselement L9 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 7, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As shown in FIGS. 17A to 17C, in the zoom lens system according toEmbodiment 8, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; and a bi-convex secondlens element L2. The first lens element L1 and the second lens elementL2 are cemented with each other.

In the zoom lens system according to Embodiment 8, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus third lens element L3 with the convex surface facingthe object side; a lens element L4 having plane incident and exitsurfaces and a reflecting surface; a bi-concave fifth lens element L5;and a bi-convex sixth lens element L6. Among these, the fifth lenselement L5 and the sixth lens element L6 are cemented with each other.

In the zoom lens system according to Embodiment 8, the third lens unitG3, in order from the object side to the image side, comprises: apositive meniscus seventh lens element L7 with the convex surface facingthe object side; a positive meniscus eighth lens element L8 with theconvex surface facing the object side; and a negative meniscus ninthlens element L9 with the convex surface facing the object side. Amongthese, the eighth lens element L8 and the ninth lens element L9 arecemented with each other.

In the zoom lens system according to Embodiment 8, the fourth lens unitG4, in order from the object side to the image side, comprises abi-convex tenth lens element L10 and a bi-concave eleventh lens elementL11. The tenth lens element L10 and the eleventh lens element L11 arecemented with each other.

In the zoom lens system according to Embodiment 8, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As shown in FIGS. 20A to 20C, in the zoom lens system according toEmbodiment 9, the first lens unit G1 comprises solely a positivemeniscus first lens element L1 with the convex surface facing the objectside.

In the zoom lens system according to Embodiment 9, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus second lens element L2 with the convex surface facingthe object side; a lens element L3 having plane incident and exitsurfaces and a reflecting surface; a bi-concave fourth lens element L4;and a bi-convex fifth lens element L5.

Further, in the zoom lens system according to Embodiment 9, the thirdlens unit G3, in order from the object side to the image side,comprises: a positive meniscus sixth lens element L6 with the convexsurface facing the object side; a bi-convex seventh lens element L7; anda bi-concave eighth lens element L8. Among these, the seventh lenselement L7 and the eighth lens element L8 are cemented with each other.

In the zoom lens system according to Embodiment 9, the fourth lens unitG4, in order from the object side to the image side, comprises: apositive meniscus ninth lens element L9 with the convex surface facingthe object side; and a bi-convex tenth lens element L10. The ninth lenselement L9 and the tenth lens element L10 are cemented with each other.

In the zoom lens system according to Embodiment 9, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As shown in FIGS. 23A to 23C, in the zoom lens system according toEmbodiment 10, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; and a positive meniscussecond lens element L2 with the convex surface facing the object side.The first lens element L1 and the second lens element L2 are cementedwith each other.

In the zoom lens system according to Embodiment 10, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus third lens element L3 with the convex surface facingthe object side; a lens element L4 having a concave incident surface anda convex exit surface and having a reflecting surface; a bi-concavefifth lens element L5; and a bi-convex sixth lens element L6.

In the zoom lens system according to Embodiment 10, the third lens unitG3, in order from the object side to the image side, comprises: apositive meniscus seventh lens element L7 with the convex surface facingthe object side; a positive meniscus eighth lens element L8 with theconvex surface facing the object side; and a negative meniscus ninthlens element L9 with the convex surface facing the object side. Amongthese, the eighth lens element L8 and the ninth lens element L9 arecemented with each other.

Furthermore, in the zoom lens system according to Embodiment 10, thefourth lens unit G4 comprises solely a positive meniscus tenth lenselement L10 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 10, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As shown in FIGS. 26A to 26C, in the zoom lens system according toEmbodiment 11, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; and a positive meniscussecond lens element L2 with the convex surface facing the object side.The first lens element L1 and the second lens element L2 are cementedwith each other.

In the zoom lens system according to Embodiment 11, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus third lens element L3 with the convex surface facingthe object side; a mirror having a reflecting surface; a bi-concavefourth lens element L4; and a bi-convex fifth lens element L5.

In the zoom lens system according to Embodiment 11, the third lens unitG3, in order from the object side to the image side, comprises: apositive meniscus sixth lens element L6 with the convex surface facingthe object side; a positive meniscus seventh lens element L7 with theconvex surface facing the object side; and a negative meniscus eighthlens element L8 with the convex surface facing the object side. Amongthese, the seventh lens element L7 and the eighth lens element L8 arecemented with each other.

Further, in the zoom lens system according to Embodiment 11, the fourthlens unit G4 comprises solely a bi-convex ninth lens element L9.

In the zoom lens system according to Embodiment 11, in zooming from thewide-angle limit to the telephoto limit, the first lens unit G1 and thethird lens unit G3 move to the object side, while the fourth lens unitG4 moves to the image side, and while the second lens unit G2 is fixedrelative to the image surface.

As described above, the zoom lens system according to Embodiments 6 to11 has a plurality of lens units each composed of at least one lenselement. However, the number of lens units constituting such a zoom lenssystem is not limited to a specific value as long as being greater thanor equal to three. That is, a four-unit construction may be employed asin Embodiments 6 to 11, while another construction is also employable.

In the zoom lens system according to Embodiments 6 to 11, an intervalbetween at least any two lens units among the plurality of lens units ischanged so that zooming is performed. Then, any one of these lens units,any one of the lens elements, or alternatively a plurality of adjacentlens elements that constitute one lens unit move in a directionperpendicular to the optical axis, so that blur caused in the image byhand blur, vibration or the like is compensated optically.

In each embodiment, as described above, when any one of a plurality oflens units, any one of the lens elements, or alternatively a pluralityof adjacent lens elements that constitute one lens unit move in adirection perpendicular to the optical axis, image blur is compensatedin such a manner that size increase in the entire zoom lens system issuppressed while excellent imaging characteristics such as smalldecentering coma aberration and decentering astigmatism are satisfied.

Here, in each embodiment, when any one of the lens units other than thesecond lens unit, any one of the lens elements other than the lenselement having a reflecting surface, or alternatively a plurality ofadjacent lens elements that are other than the lens element having areflecting surface and that constitute one lens unit move in a directionperpendicular to the optical axis, the entire zoom lens system can beconstructed more compactly. Further, image blur can be compensated in astate that excellent imaging characteristics are satisfied. Thus, thisconstruction is preferable. More preferably, any one of the lens unitsother than the second lens unit moves in a direction perpendicular tothe optical axis.

Furthermore, in each embodiment, when the third lens unit located on themost object side among the subsequent lens units moves in a directionperpendicular to the optical axis, the entire zoom lens system can beconstructed remarkably compactly. Further, image blur can be compensatedin a state that excellent imaging characteristics are satisfied. Thus,this construction is remarkably preferable.

Conditions are described below that are preferably satisfied by a zoomlens system like the zoom lens system according to Embodiments 6 to 11,in order from the object side to the image side, comprising: a firstlens unit having positive optical power; a second lens unit thatincludes a lens element having a reflecting surface for bending a lightbeam from an object and that has negative optical power; and subsequentlens units including at least one lens unit having positive opticalpower, wherein any one of the lens units, any one of the lens elements,or alternatively a plurality of adjacent lens elements that constituteone lens unit move in a direction perpendicular to the optical axis.Here, a plurality of preferable conditions are set forth for the zoomlens system according to each embodiment. The construction thatsatisfies all the plural conditions is most desirable for the zoom lenssystem. However, when an individual condition is satisfied, a zoom lenssystem providing the corresponding effect can be obtained.

For example, in a zoom lens system like the zoom lens system accordingto Embodiments 6 to 11, the following condition (1) is satisfied;1.50<M ₁ /f _(W)<3.00   (1)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

f_(W) is a focal length of the entire zoom lens system at the wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at the telephotolimit.

The condition (1) sets forth the amount of optical axial movement of thefirst lens unit, and hence determines the thickness of the zoom lenssystem in the imaging state. When the value exceeds the upper limit ofthe condition (1), the amount of optical axial movement of the firstlens unit increases, and so does the optical overall length at atelephoto limit. This causes an increase in the thickness of the zoomlens system, and hence prevents compact construction. In contrast, whenthe value goes below the lower limit of the condition (1), aberrationfluctuation becomes large in the entire zoom lens system. This situationis undesirable.

Here, when at least one of the following conditions (1)′ and (1)″ issatisfied, the above effect is achieved more successfully.2.10<M ₁ /f _(W)   (1)′M ₁ /f _(W)<2.40   (1)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 6 to 11, when the subsequent lens units, inorder from the object side to the image side, comprise a third lens unithaving positive optical power and a fourth lens unit having positiveoptical power, it is preferable that the following condition (2) issatisfied;3.20<f ₃ /f _(W)<4.00   (2)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₃ is a composite focal length of the third lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The above condition (2) sets forth the focal length of the third lensunit. When the value exceeds the upper limit of the condition (2),aberration generated in the third lens unit becomes excessive, and hencecauses difficulty in compensating coma aberration generated in theentire zoom lens system. In contrast, when the value goes below thelower limit of the condition (2), a tendency arises that the amount ofmovement of the lens unit at the time of focusing becomes large or thatthe amount of movement of the lens unit or lens element that moves in adirection perpendicular to the optical axis at the time of image blurcompensation becomes large.

Here, when the following condition (2)′ or (2)″ is satisfied, the aboveeffect is achieved more successfully.3.30<f ₃ /f _(W)   (2)′3.70<f ₃ /f _(W)   (2)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 6 to 11, when the subsequent lens units, inorder from the object side to the image side, comprise a third lens unithaving positive optical power and a fourth lens unit having positiveoptical power, it is preferable that the following condition (3) issatisfied;0.40<f ₃ /f _(T)<0.90   (3)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₃ is the composite focal length of the third lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The above condition (3) sets forth the focal length of the third lensunit. When the value exceeds the upper limit of the condition (3),aberration generated in the third lens unit becomes excessive, and hencecauses difficulty in compensating coma aberration generated in theentire zoom lens system. In contrast, when the value goes below thelower limit of the condition (3), a tendency arises that the amount ofmovement of the lens unit at the time of focusing becomes large or thatthe amount of movement of the lens unit or lens element that moves in adirection perpendicular to the optical axis at the time of image blurcompensation becomes large.

Here, when the following condition (3)′ or (3)41 is satisfied, the aboveeffect is achieved more successfully.f ₃ /f _(T)<0.75   (3)′f ₃ /f _(T)<0.65   (3)

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 6 to 11, when the subsequent lens units, inorder from the object side to the image side, comprise a third lens unithaving positive optical power and a fourth lens unit having positiveoptical power, it is preferable that the following condition (4) issatisfied;0.40<D ₃ /f _(W)<1.20   (4)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

D₃ is an optical axial thickness of the third lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (4) sets forth the optical axial thickness of the thirdlens unit. When the value exceeds the upper limit of the condition (4),the optical axial thickness of the third lens unit increases, and sodoes the overall length of the zoom lens system. Thus, providing of acompact lens barrel, a compact imaging device or a compact camerabecomes difficult. In contrast, when the value goes below the lowerlimit of the condition (4), a tendency arises that the aberrationfluctuation of the entire zoom lens system becomes large.

Here, when the following condition (4)′ or (4)″ is satisfied, the aboveeffect is achieved more successfully.0.40<D ₃ /f _(W)<0.70   (4)′1.00<D ₃ /f _(W)<1.10 (4)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 6 to 11, when the third lens unit located onthe most object side among the subsequent lens units moves in adirection perpendicular to the optical axis, it is preferable that thefollowing condition (5) is satisfied;0.10<f _(W) /Y _(W)×10⁻³<0.20   (5)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

Y_(W) is an amount of movement of the third lens unit at the time ofmaximum blur compensation in a focal length f_(W) of the entire zoomlens system at the wide-angle limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The above condition (5) relates to the amount of movement of the thirdlens unit at the time of blur compensation. When the value exceeds theupper limit of the condition (5), a difficulty arises in sufficientcompensation of image blur caused by hand blur, vibration or the like.In contrast, when the value goes below the lower limit of the condition(5), compensation becomes excessive. This can cause degradation in theoptical performance.

Here, when at least one of the following conditions (5)′ and (5)″ issatisfied, the above effect is achieved more successfully.0.12<f _(W) /Y _(W)×10⁻³   (5)′f _(W) /Y _(W)×10⁻³<0.17   (5)

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 6 to 11, when the third lens unit located onthe most object side among the subsequent lens units moves in adirection perpendicular to the optical axis, it is preferable that thefollowing condition (6) is satisfied;0.20<f _(T) /Y _(T)×10⁻³<0.35   (6)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

Y_(T) is an amount of movement of the third lens unit at the time ofmaximum blur compensation in a focal length f_(T) of the entire zoomlens system at the telephoto limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The above condition (6) relates to the amount of movement of the thirdlens unit at the time of blur compensation. When the value exceeds theupper limit of the condition (6), a difficulty arises in sufficientcompensation of image blur caused by hand blur, vibration or the like.In contrast, when the value goes below the lower limit of the condition(6), compensation becomes excessive. This can cause degradation in theoptical performance.

Here, when at least one of the following conditions (6)′ and (6)″ issatisfied, the above effect is achieved more successfully.0.23<f _(T) /Y _(T)×10⁻³   (6)′f_(T) /Y _(T)×10⁻³<0.29   (6)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, when a lens barrel that holds a zoom lens systemlike the zoom lens system according to Embodiments 6 to 11 is applied toan imaging device where as in Embodiments 1 to 5, in the imaging state,the first lens unit is held in a manner movable in a direction of thelight beam from the object, while in the accommodated state, the secondlens unit escapes in the optical axis direction toward the image side ofthe imaging optical system, the zoom lens system is preferred to satisfythe following condition (7);0.50<Σ D ₁₂ /Σ d _(AIR)<1.00   (7)

where,

Σ D₁₂ is an optical axial total thickness of the first lens unit and thesecond lens unit, and

Σ d_(AIR) is an optical axial total air space between the respectivelens units that are located on the image side relative to the secondlens unit and that move in the optical axis direction in zooming.

The condition (7) relates to the thickness of the imaging device in theaccommodated state. When the value exceeds the upper limit of thecondition (7), the escaped optical element becomes large, and hencecauses a tendency of increase in the size of the imaging device. Incontrast, when the value goes below the lower limit of the condition(7), sufficient compensation of aberration becomes difficult in theentire zoom lens system.

Here, when the following condition (7)′ is satisfied, the above effectis achieved more successfully.0.75<Σ D ₁₂ /Σ d _(AIR)<1.00   (7)′

Further, for example, as in the zoom lens system according toEmbodiments 6 to 11, in a zoom lens system comprising, in order from theobject side to the image side, comprising a first lens unit havingpositive optical power and a second lens unit having negative opticalpower, in which the second lens unit includes a lens element having areflecting surface, it is preferable that the following condition (8) issatisfied;1.20<d _(R) ·f _(W) /d ₂<1.70   (8)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

d_(R) is an interval between the most object side lens element in thesecond lens unit and the lens element having a reflecting surface,

d₂ is an interval between the most object side lens element in thesecond lens unit and a lens element on the image side relative to thereflecting surface in the second lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (8) is a condition for achieving satisfactory imagingcharacteristics and realizing size reduction in the zoom lens system.When the value exceeds the upper limit of the condition (8), imagingperformance degrades in the periphery part. Thus, in order that theimaging performance should be improved, this causes a tendency of sizeincrease in the entire zoom lens system. In contrast, when the valuegoes below the lower limit of the condition (8), because of a reflectingsurface, horizontal bending of the optical path becomes difficult.

Here, when at least one of the following conditions (8)′ and (8)″ issatisfied, the above effect is achieved more successfully.1.20<d _(R) ·f _(W) /d ₂<1.45   (8)′1.50<d _(R) ·f _(W) /d ₂<1.70   (8)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, as in the zoom lens system according toEmbodiments 6 to 11, in a zoom lens system comprising, in order from theobject side to the image side, comprising a first lens unit havingpositive optical power and a second lens unit having negative opticalpower, in which the second lens unit includes a lens element having areflecting surface, it is preferable that the following condition (9) issatisfied;−2.50<f ₂ /f _(W<)−2.00   (9)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₂ is a composite focal length of the second lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (9) relates to the error sensitivity of the second lensunit moved in the accommodated state of the imaging device. When thevalue exceeds the upper limit of the condition (9), aberration generatedin the second lens unit becomes excessive, and hence causes difficultyin compensating coma aberration generated in the entire zoom lenssystem. In contrast, when the value goes below the lower limit of thecondition (9), the necessary effective diameter becomes large in thefirst lens unit. This causes a tendency of size increase in the entirezoom lens system.

Here, when at least one of the following conditions (9)′ and (9)″ issatisfied, the above effect is achieved more successfully.−2.50<f ₂ /f _(W)<−2.30   (9)′−2.20<f ₂ /f _(W)<−2.00   (9)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, as in the zoom lens system according toEmbodiments 6 to 11, in a zoom lens system comprising, in order from theobject side to the image side, comprising a first lens unit havingpositive optical power and a second lens unit having negative opticalpower, in which the second lens unit includes a lens element having areflecting surface, it is preferable that the following condition (10)is satisfied;6.50<f ₁ /f _(W)<8.50   (10)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₁ is a composite focal length of the first lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (10) relates to the size of the reflecting surface movedin the accommodated state of the imaging device. When the value exceedsthe upper limit of the condition (10), necessary reflecting surfacebecomes large. This causes a tendency of size increase in the entiresecond lens unit and hence in the entire zoom lens system. In contrast,when the value goes below the lower limit of the condition (10), thesize of the reflecting surface can be reduced. Nevertheless, a tendencyarises that sufficient compensation of aberration becomes difficult.

Here, when at least one of the following conditions (10)′ and (10)″ issatisfied, the above effect is achieved more successfully.8.10<f ₁ /f _(W)<8.50   (10)′6.50<f ₁ /f _(W)<6.80   (10)″

-   -   (here, Z =f_(T)/f_(W)>3.90)

Further, for example, as in the zoom lens system according toEmbodiments 6 to 11, in a zoom lens system comprising, in order from theobject side to the image side, comprising a first lens unit havingpositive optical power and a second lens unit having negative opticalpower, in which the second lens unit includes a lens element having areflecting surface, it is preferable that the following condition (11)is satisfied;0.50<M ₁ /M ₃<0.70   (11)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is an amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

M₃ is an amount of optical axial movement of the third lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (11) sets forth the amount of optical axial movement ofthe first lens unit, and hence determines the thickness of the imagingdevice in the imaging state. When the value exceeds the upper limit ofthe condition (11), the amount of optical axial movement of the firstlens unit increases and so does the optical overall length at atelephoto limit. Thus, the amount of draw-out of the first lens unitbecomes large, so that a tendency arises that the mechanism of the lensbarrel for holding the zoom lens system becomes complicated. Incontrast, when the value goes below the lower limit of the condition(11), it becomes difficult to ensure a desired zoom ratio and excellentimaging characteristics.

Here, when at least one of the following conditions (11)′ and (11)″ issatisfied, the above effect is achieved more successfully.0.54<M ₁ /M ₃   (11)′M ₁ /M ₃<0.64   (11)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

Further, for example, as in the zoom lens system according toEmbodiments 6 to 11, in a zoom lens system comprising, in order from theobject side to the image side, comprising a first lens unit havingpositive optical power and a second lens unit having negative opticalpower, in which the second lens unit includes a lens element having areflecting surface, it is preferable that the following condition (12)is satisfied;1.50<M ₁ /I<2.50   (12)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

M₁ is the amount of optical axial movement of the first lens unit at thetime of zooming from the wide-angle limit to the telephoto limit,

I is a diagonal length of the image sensorI=2×f _(W)×tan ω_(W)×0.60,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit,

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit, and

ω_(W) is an incident half view angle at the wide-angle limit.

The condition (12) sets forth the amount of optical axial movement ofthe first lens unit, and hence determines the thickness of the imagingdevice. When the value exceeds the upper limit of the condition (12),the amount of optical axial movement of the first lens unit increases,and so does the optical overall length at a telephoto limit. This causesa tendency that the imaging device becomes large in the thicknessdirection. In contrast, when the value goes below the lower limit of thecondition (12), a tendency arises that the aberration fluctuation of theentire zoom lens system becomes large.

Here, when at least one of the following conditions (12)′ and (12)″ issatisfied, the above effect is achieved more successfully.1.80<M ₁ /I   (12)′M₁ /I<2.00   (12)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 6 to11, it is preferable that the following condition (13) is satisfied;2.50<f ₄ /f _(W)<4.00   (13)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₄ is a composite focal length of the fourth lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (13) sets forth the focal length of the fourth lens unit.When the value exceeds the upper limit of the condition (13), it becomesdifficult that spherical aberration and surface curvature arecompensated with satisfactory balance in the entire zoom lens system. Incontrast, when the value goes below the lower limit of the condition(13), a tendency arises that the amount of movement at the time offocusing becomes large.

Here, when at least one of the following conditions (13)′ and (13)″ issatisfied, the above effect is achieved more successfully.2.90<f ₄ /f _(W)   (13)′f ₄ /f _(W)<3.30   (13)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 6 to11, it is preferable that the following condition (14) is satisfied;1.20<β_(T4)/βhd W4<1.90   (14)

-   -   (here, Z=f_(T)/f_(W)>3.90, β_(T4)/β_(W4)≠0)

where,

β_(T4) is a magnification of the fourth lens unit in the infinityin-focus condition at a telephoto limit,

β_(W4) is a magnification of the fourth lens unit in the infinityin-focus condition at a wide-angle limit,

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit, and

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit.

The condition (14) sets forth the magnification variation in the fourthlens unit, and hence sets forth zoom contribution of the fourth lensunit. When the value exceeds the upper limit of the condition (14), itbecomes difficult that aberration is compensated in the entire zoom lenssystem with satisfactory balance. In contrast, when the value goes belowthe lower limit of the condition (14), a desired zoom ratio becomesdifficult to be obtained.

Here, when at least one of the following conditions (14)′ and (14)″ issatisfied, the above effect is achieved more successfully.1.40<β_(T4)/β_(W4)   (14)′β_(T4)/β_(W4)<1.60   (14)″

-   -   (here, Z=f_(T)/f_(W)>3.90, β_(T4)/β_(W4)–0)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 6 to11, it is preferable that the following condition (15) is satisfied;0.90<f ₃ /f ₄<1.50   (15)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₃ is the composite focal length of the third lens unit,

f₄ is the composite focal length of the fourth lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (15) sets forth the ratio of the focal lengths of thethird lens unit and the fourth lens unit, and hence sets forth thefunction of each lens unit in zooming. When the value exceeds the upperlimit of the condition (15), zooming effect decreases in the third lensunit. Thus, a desired zoom ratio becomes difficult to be obtained. Incontrast, when the value goes below the lower limit of the condition(15), it becomes difficult that astigmatism is compensated in the entirezoom lens system.

Here, when at least one of the following conditions (15)′ and (15)″ issatisfied, the above effect is achieved more successfully.1.30<f ₃ /f ₄<1.50   (15)′0.90<f ₃ /f ₄<1.15   (15)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; and subsequent lensunits including at least one lens unit having positive optical power,wherein a lens element having a reflecting surface is included in thesecond lens unit, as in the zoom lens system according to Embodiments 6to 11, it is preferable that the following condition (16) is satisfied;−4.00<f ₁ /f ₂<−3.00   (16)

-   -   (here, Z=f_(T)/f_(W)>3.90)

where,

f₁ is the composite focal length of the first lens unit,

f₂ is the composite focal length of the second lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (16) sets forth the focal length ratio of the first lensunit and the second lens unit. When the value exceeds the upper limit ofthe condition (16), a tendency arises that the necessary effectivediameter becomes large in the second lens unit, so that a size increaseis caused in the entire zoom lens system. In contrast, when the valuegoes below the lower limit of the condition (16), aberration generatedin the second lens unit becomes excessive, and hence causes difficultyin sufficiently compensating aberration in the entire zoom lens system.

Here, when at least one of the following conditions (16)′ and (16)″ issatisfied, the above effect is achieved more successfully.−3.40<f ₁ /f ₂   (16)′f ₁ /f ₂<−3.20   (16)″

-   -   (here, Z=f_(T)/f_(W)>3.90)

The zoom lens system according to each of Embodiments 6 to 11 has been azoom lens system of four units having a construction of positive,negative, positive and positive, in order from the object side to theimage side, comprising: a first lens unit G1 having positive opticalpower; a second lens unit G2 having negative optical power; a diaphragmA; a third lens unit G3 having positive optical power; and a fourth lensunit G4 having positive optical power. However, the present invention isnot limited to this construction. For example, the employed constructionmay be: a three-unit construction of positive, negative and positive; afour-unit construction of positive, negative, positive and negative; oralternatively a five-unit construction of positive, negative, positive,positive and positive, or of positive, negative, positive, positive andnegative, or of positive, negative, positive, negative and positive.That is, as long as comprising a first lens unit having positive opticalpower, a second lens unit having negative optical power, and subsequentlens units that include at least one lens unit having positive opticalpower, any zoom lens system may be applied suitably to the imagingdevice, for example, according to Embodiments 1 to 5.

Here, the lens units constituting the zoom lens system of Embodiments 6to 11 are composed exclusively of refractive type lens elements thatdeflect the incident light by refraction (that is, lens elements of atype in which deflection is achieved at the interface between media eachhaving a distinct refractive index). However, the present invention isnot limited to the zoom lens system of this construction. For example,the lens units may employ diffractive type lens elements that deflectthe incident light by diffraction; refractive-diffractive hybrid typelens elements that deflect the incident light by a combination ofdiffraction and refraction; or gradient index type lens elements thatdeflect the incident light by distribution of refractive index in themedium.

An imaging device comprising a zoom lens system according to Embodiments6 to 11 described above and an image sensor such as a CCD or a CMOSmaybe applied to a mobile telephone, a PDA (Personal DigitalAssistance), a surveillance camera in a surveillance system, a Webcamera, a vehicle-mounted camera or the like.

Further, the construction of the digital still camera and the zoom lenssystem according to Embodiments 6 to 11 described above is applicablealso to a digital video camera for moving images. In this case, movingimages with high resolution can be acquired in addition to still images.

Hereinafter, numerical examples which are actual implementations of thezoom lens systems according to Embodiments 6 to 11 will be described. Inthe numerical examples, the units of the length in the tables are all“mm”. Moreover, in the numerical examples, r is the radius of curvature,d is the axial distance, nd is the refractive index to the d-line, andνd is the Abbe number to the d-line. In the numerical examples, thesurfaces marked with * are aspherical surfaces, and the asphericalsurface configuration is defined by the following expression:

$z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {Dh}^{4} + {Eh}^{6} + {Fh}^{8} + {Gh}^{10}}$Here, κ is the conic constant, D, E, F and G are a fourth-order,sixth-order, eighth-order and tenth-order aspherical coefficients,respectively.

FIGS. 12A to 12I are longitudinal aberration diagrams of a zoom lenssystem according to Example 1. FIGS. 15A to 15I are longitudinalaberration diagrams of a zoom lens system according to Example 2. FIGS.18A to 18I are longitudinal aberration diagrams of a zoom lens systemaccording to Example 3. FIGS. 21A to 21I are longitudinal aberrationdiagrams of a zoom lens system according to Example 4. FIGS. 24A to 24Iare longitudinal aberration diagrams of a zoom lens system according toExample 5. FIGS. 27A to 27I are longitudinal aberration diagrams of azoom lens system according to Example 6.

FIGS. 12A to 12C, 15A to 15C, 18A to 18C, 21A to 21C, 24A to 24C and 27Ato 27C show the longitudinal aberration at the wide-angle limit. FIGS.12D to 12F, 15D to 15F, 18D to 18F, 21D to 21F, 24D to 24F, and 27D to27F show the longitudinal aberration at the middle position. FIGS. 12Gto 12I, 15G to 15I, 18G to 18I, 21G to 21I, 24G to 24I, and 27G to 27Ishow the longitudinal aberration at the telephoto limit. FIGS. 12A, 12D,12G, 15A, 15D, 15G, 18A, 18D, 18G, 21A, 21D, 21G, 24A, 24D, 24G, 27A,27D and 27G are spherical aberration diagrams. FIGS. 12B, 12E, 12H, 15B,15E, 15H, 18B, 18E, 18H, 21B, 21E, 21H, 24B, 24E, 24H, 27B, 27E and 27Hare astigmatism diagrams. FIGS. 12C, 12F, 12I, 15C, 15F, 15I, 18C, 18F,18I, 21C, 21F, 21I, 24C, 24F, 24I, 27C, 27F and 27I are distortiondiagrams. In each spherical aberration diagram, the vertical axisindicates the F-number, and the solid line, the short dash line and thelong dash line indicate the characteristics to the d-line, the F-lineand the C-line, respectively. In each astigmatism diagram, the verticalaxis indicates the half view angle, and the solid line and the dash lineindicate the characteristics to the sagittal image plane (in each Fig.,indicated as “s”) and the meridional image plane (in each Fig.,indicated as “m”), respectively. In each distortion diagram, thevertical axis indicates the half view angle.

FIGS. 13A to 13F are lateral aberration diagrams of a zoom lens systemaccording to Example 1 at the telephoto limit. FIGS. 16A to 16F arelateral aberration diagrams of a zoom lens system according to Example 2at the telephoto limit. FIGS. 19A to 19F are lateral aberration diagramsof a zoom lens system according to Example 3 at the telephoto limit.FIGS. 22A to 22F are lateral aberration diagrams of a zoom lens systemaccording to Example 4 at the telephoto limit. FIGS. 25A to 25F arelateral aberration diagrams of a zoom lens system according to Example 5at the telephoto limit. FIGS. 28A to 28F are lateral aberration diagramsof a zoom lens system according to Example 6 at the telephoto limit.

FIGS. 13A to 13C, 16A to 16C, 19A to 19C, 22A to 22C, 25A to 25C, and28A to 28C are lateral aberration diagrams at the telephoto limitcorresponding to a basic state that image blur compensation is notperformed. FIGS. 13D to 13F, 16D to 16F, 19D to 19F, 22D to 22F, 25D to25F, and 28D to 28F are lateral aberration diagrams corresponding to animage blur compensation state at the telephoto limit in which theentirety of the third lens unit G3 is moved by a predetermined amount ina direction perpendicular to the optical axis. Among the lateralaberration diagrams of the basic state, FIGS. 13A, 16A, 19A, 22A, 25A,and 28A show the lateral aberration at an image point at 75% of themaximum image height. FIGS. 13B, 16B, 19B, 22B, 25B, and 28B show thelateral aberration at the axial image point. FIGS. 13C, 16C, 19C, 22C,25C, and 28C show the lateral aberration at an image point at −75% ofthe maximum image height. Among the lateral aberration diagrams of theimage blur compensation state, FIGS. 13D, 16D, 19D, 22D, 25D, and 28Dshow the lateral aberration at an image point at 75% of the maximumimage height. FIGS. 13E, 16E, 19E, 22E, 25E, and 28E show the lateralaberration at the axial image point. FIGS. 13F, 16F, 19F, 22F, 25F, and28F show the lateral aberration at an image point at −75% of the maximumimage height. In each lateral aberration diagram, the horizontal axisindicates the distance from the principal ray on the pupil surface, andthe solid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In the lateral aberration diagrams of FIGS. 13A to 13F, 16A to 16F, 19Ato 19F, 22A to 22F, 25A to 25F, and 28A to 28F, the meridional imageplane is adopted as the plane containing the optical axis of the firstlens unit G1 and the optical axis of the third lens unit G3.

Here, the amount of movement in a direction perpendicular to the opticalaxis of the third lens unit G3 in the image blur compensation state is0.138 mm in Example 1, 0.132 mm in Example 2, 0.160 mm in Example 3,0.081 mm in Example 4, 0.107 mm in Example 5, and 0.097 mm in Example 6.Here, the amount of image decentering in a case that the zoom lenssystem inclines by 0.3° when the shooting distance is infinity at thetelephoto limit is equal to the amount of image decentering in a casethat the entirety of the third lens unit G3 moves in parallel in adirection perpendicular to the optical axis by each of the above values.

As seen from the lateral aberration diagrams, satisfactory symmetry isobtained in the lateral aberration at the axial image point. Further,when the lateral aberration at the +75% image point and the lateralaberration at the −75% image point are compared with each other in thebasic state, all have a small degree of curvature and almost the sameinclination in the aberration curve. Thus, decentering coma aberrationand decentering astigmatism are small. This indicates that sufficientimaging performance is obtained even in the image blur compensationstate. Further, when the image blur compensation angle of a zoom lenssystem is the same, the amount of parallel movement required for imageblur compensation decreases with decreasing focal length of the entirezoom lens system. Thus, at arbitrary zoom positions, sufficient imageblur compensation can be performed for image blur compensation angles upto 0.3° without degrading the imaging characteristics.

EXAMPLE 1

A zoom lens system of Example 1 corresponds to Embodiment 6 shown inFIGS. 11A to 11C. Table 1 shows the lens data of the zoom lens system ofExample 1. Table 2 shows the focal length, the F-number, the half viewangle and the variable axial distance data, when the shooting distanceis infinity. Table 3 shows the aspherical data.

TABLE 1 Lens Lens unit element Surface r d nd νd G1 L1 1 25.448 3.8351.72916 54.70 2 261.863 Variable G2 L2 3 52.775 1.000 1.83400 37.30 48.288 3.508 L3 5 ∞ 11.000  1.58913 61.30 6 ∞ 0.323 L4 7 −69.338 0.8001.80470 41.00 8 14.737* 0.792 L5 9 19.229 2.300 1.84666 23.80 10 −49.225Variable Diaphragm 11 ∞ 0.900 G3 L6 12 7.552 1.800 1.72916 54.70 1347.305 1.619 L7 14 8.803* 1.900 1.66547 55.20 L8 15 −87.326 0.7001.84666 23.80 16 5.147 Variable G4 L9 17 8.381* 0.876 1.66547 55.20  L1018 8.456 1.990 1.75520 27.50 19 28.138 Variable P 20 ∞ 2.100 1.5168064.20 21 ∞

TABLE 2 Axial Wide-angle Middle Telephoto distance limit position limitd2 0.800 9.500 13.037 d10 23.521 14.525 1.400 d16 2.799 13.046 26.980d19 4.565 3.254 2.514 f 5.76 13.76 32.97 F 2.92 3.96 5.86 ω 30.33 13.115.64

TABLE 3 Surface κ D E F G 8 0.00E+00 −8.41E−05 1.16E−06 −5.72E−088.15E−10 14 0.00E+00 −3.60E−04 −1.68E−05     1.40E−06 −9.77E−08   170.00E+00   9.09E−06 2.92E−06 −1.42E−07 2.86E−09

EXAMPLE 2

A zoom lens system of Example 2 corresponds to Embodiment 7 shown inFIGS. 14A to 14C. Table 4 shows the lens data of the zoom lens system ofExample 2. Table 5 shows the focal length, the F-number, the half viewangle and the variable axial distance data, when the shooting distanceis infinity. Table 6 shows the aspherical data.

TABLE 4 Lens Lens unit element Surface r d nd νd G1 L1 1 25.170 0.8001.84666 23.80 L2 2 20.432 3.922 1.77250 49.60 3 153.216 Variable G2 L3 437.493 1.000 1.83400 37.30 5 7.502 4.205 L4 6 ∞ 11.000  1.58913 61.30 7∞ 0.273 L5 8 −1000.000* 1.200 1.60602 57.40 9 13.505* 0.688 L6 10 28.1532.000 1.80518 25.50 11 −48.157 Variable Diaphragm 12 ∞ 0.900 G3 L7 135.350 2.077 1.66547 55.20 14 90.833* 0.200 L8 15 8.731 0.600 1.8466623.80 16 4.227 Variable G4 L9 17 9.383 1.935 1.74330 49.20 18 20.334Variable P 19 ∞ 2.100 1.51680 64.20 20 ∞

TABLE 5 Axial Wide-angle Middle Telephoto distance limit position limitd3 0.700 9.500 13.740 d11 23.381 13.024 1.300 d16 1.000 13.181 27.730d18 8.264 6.395 3.625 F 5.74 13.77 33.00 F 2.99 3.99 5.88 ω 30.36 13.055.49

TABLE 6 Surface κ D E F G 8 0.00E+00 −2.36E−04 −8.10E−06 6.94E−07−1.02E−08 9 0.00E+00 −3.97E−04 −7.45E−06 7.17E−07 −1.15E−08 14 0.00E+00−4.48E−04   1.08E−06 −1.96E−06     7.01E−08

EXAMPLE 3

A zoom lens system of Example 3 corresponds to Embodiment 8 shown inFIGS. 17A to 17C. Table 7 shows the lens data of the zoom lens system ofExample 3. Table 8 shows the focal length, the F-number, the half viewangle and the variable axial distance data, when the shooting distanceis infinity. Table 9 shows the aspherical data.

TABLE 7 Lens Lens unit element Surface R d nd νd G1 L1 1 28.527 1.0001.84666 23.80 L2 2 19.210 4.852 1.72916 54.70 3 −2048.605 Variable G2 L34 82.350 1.000 1.83400 37.30 5 7.653 4.047 L4 6 ∞ 11.000  1.84666 23.807 ∞ 0.135 L5 8 −64.776* 0.800 1.80470 41.00 L6 9 50.007 2.660 1.8466623.80 10 −39.632 Variable Diaphragm 11 ∞ 0.900 G3 L7 12 7.092 1.8001.72916 54.70 13 22.978 1.619 L8 14 9.166* 1.900 1.66547 55.20 L9 1511.908 0.700 1.84666 23.80 16 5.080 Variable G4  L10 17 8.796* 2.9061.66547 55.20  L11 18 −13.268 0.800 1.75520 27.50 19 57.700 Variable P20 ∞ 2.100 1.51680 64.20 21 ∞

TABLE 8 Axial Wide-angle Middle Telephoto distance limit position limitd3 0.800 8.731 16.000 d10 27.000 11.943 1.400 d16 1.000 17.531 31.567d19 5.205 3.688 0.334 f 5.75 16.00 44.96 F 2.90 4.54 6.99 ω 30.35 11.893.99

TABLE 9 Surface κ D E F G 8 0.00E+00 7.58E−05 −2.34E−07 1.75E−08−7.34E−11 14 0.00E+00 −4.02E−04   −2.80E−05 2.61E−06 −1.29E−07 170.00E+00 8.91E−05   1.14E−06 −6.30E−08     1.64E−09

EXAMPLE 4

A zoom lens system of Example 4 corresponds to Embodiment 9 shown inFIGS. 20A to 20C. Table 10 shows the lens data of the zoom lens systemof Example 4. Table 11 shows the focal length, the F-number, the halfview angle and the variable axial distance data, when the shootingdistance is infinity. Table 12 shows the aspherical data.

TABLE 10 Lens Lens unit element Surface r d nd νd G1 L1 1 32.527 3.221.72916 54.7 2 906.538 Variable G2 L2 3 37.780 1.00 1.83400 37.3 4 7.1934.68 L3 5 ∞ 11.00  1.58913 61.3 6 ∞ 1.05 L4 7 −21.970 0.80 1.80470 41.08 31.346* 0.79 L5 9 93.774 2.30 1.84666 23.8 10 −17.204 VariableDiaphragm 11 ∞ 0.90 G3 L6 12 8.134 1.80 1.72916 54.7 13 73.790 1.62 L714 8.668* 1.90 1.66547 55.2 L8 15 −105.445 0.70 1.84666 23.8 16 5.355Variable G4 L9 17 12.625* 1.35 1.66547 55.2  L10 18 22.184 1.55 1.7552027.5 19 −75.170 Variable P 20 ∞ 2.10 1.51680 64.2 21 ∞

TABLE 11 Axial Wide-angle Middle Telephoto distance limit position limitd2 0.800 9.500 11.330 d10 18.440 8.755 1.400 d16 6.380 18.235 26.820 d194.130 1.835 0.781 f 5.73 13.76 22.85 F 3.20 4.86 6.47 ω 30.42 12.98 7.93

TABLE 12 Surface κ D E F G 8 0.00E+00 −9.49E−05 −1.73E−06   1.36E−07−3.68E−09   14 0.00E+00 −3.00E−04 −6.37E−06 −1.00E−06 9.39E−08 170.00E+00   1.94E−05   6.71E−06 −3.42E−07 6.21E−09

EXAMPLE 5

A zoom lens system of Example 5 corresponds to Embodiment 10 shown inFIGS. 23A to 23C. Table 13 shows the lens data of the zoom lens systemof Example 5. Table 14 shows the focal length, the F-number, the halfview angle and the variable axial distance data, when the shootingdistance is infinity. Table 15 shows the aspherical data.

TABLE 13 Lens Lens unit element Surface r d nd νd G1 L1 1 30.146 1.0001.84666 23.80 L2 2 24.093 3.822 1.72916 54.70 3 847.959 Variable G2 L3 465.932 1.000 1.83400 37.30 5 8.435 3.723 L4 6 −70.264 11.000  1.5891361.30 7 −101.023 0.328 L5 8 −40.497 0.800 1.80470 41.00 9 23.976* 0.792L6 10 26.632 2.300 1.84666 23.80 11 −46.328 Variable Diaphragm 12 ∞0.900 G3 L7 13 7.710 1.800 1.72916 54.70 14 45.669 1.619 L8 15 8.006*1.900 1.66547 55.20 L9 16 28.942 0.700 1.84666 23.80 17 4.869 VariableG4  L10 18 10.544* 1.756 1.66547 55.20 19 139.806 Variable P 20 ∞ 2.1001.51680 64.20 21 ∞

TABLE 14 Axial Wide-angle Middle Telephoto distance limit position limitd3 0.800 10.500 14.012 d11 22.523 14.021 1.400 d17 3.989 14.766 28.645d19 5.253 2.933 1.722 f 5.74 13.76 32.95 F 3.01 4.31 6.87 ω 30.43 12.955.57

TABLE 15 Surface κ D E F G 9 0.00E+00 −4.78E−05 8.51E−07 −3.42E−085.39E−10 15 0.00E+00 −4.20E−04 1.41E−05 −4.43E−06 2.49E−07 18 0.00E+00  6.57E−05 9.97E−06 −6.71E−07 1.70E−08

EXAMPLE 6

A zoom lens system of Example 6 corresponds to Embodiment 11 shown inFIGS. 26A to 26C. Table 16 shows the lens data of the zoom lens systemof Example 6. Table 17 shows the focal length, the F-number, the halfview angle and the variable axial distance data, when the shootingdistance is infinity. Table 18 shows the aspherical data.

TABLE 16 Lens Lens unit element Surface r d nd νd G1 L1 1 32.413 1.0001.84666 23.80 L2 2 27.101 3.415 1.72916 54.70 3 832.594 Variable G2 L3 448.603 1.000 1.83400 37.30 5 8.534 3.347 Mirror 6 ∞ 11.000  7 ∞ 0.556 L48 −49.344 0.800 1.80470 41.00 9 20.487* 0.792 L5 10 28.257 2.300 1.8466623.80 11 −43.722 Variable Diaphragm 12 ∞ 0.900 G3 L6 13 7.797 1.8001.72916 54.70 14 50.171 1.619 L7 15 7.948* 1.900 1.66547 55.20 L8 1641.823 0.700 1.84666 23.80 17 4.929 Variable G4 L9 18 12.630* 1.6941.66547 55.20 19 −425.235 Variable P 20 ∞ 2.100 1.51680 64.20 21 ∞

TABLE 17 Axial Wide-angle Middle Telephoto distance limit position limitd3 0.800 10.500 13.657 d11 22.053 13.593 0.230 d17 4.624 16.078 30.532d19 5.303 2.276 1.216 f 5.75 13.76 32.98 F 3.15 4.65 7.55 ω 30.40 12.965.59

TABLE 18 Surface κ D E F G 9 0.00E+00 −6.93E−05 1.24E−07 −4.12E−093.88E−12 15 0.00E+00 −4.08E−04 1.12E−05 −3.38E−06 1.56E−07 18 0.00E+00  1.07E−04 8.43E−06 −5.49E−07 1.42E−08

The corresponding values to the above conditions are listed in thefollowing Table 19.

TABLE 19 Example Condition 1 2 3 4 5 6 (1) M₁/f_(w) 2.13 2.27 2.64 1.842.30 2.24 (2) f₃/f_(w) 3.59 3.77 3.87 3.48 3.33 3.28 (3) f₃/f_(T) 0.630.66 0.49 0.87 0.58 0.57 (4) D₃/f_(w) 1.05 0.50 1.05 1.05 1.05 1.05 (5)f_(w)/Y_(w) × 10⁻³ 0.13 0.13 0.12 0.15 0.15 0.16 (6) f_(T)/Y_(T) × 10⁻³0.24 0.25 0.28 0.28 0.31 0.34 (7) ΣD₁₂/Σd_(AIR) 0.76 0.77 0.77 0.86 0.780.76 (8) d_(R) · f_(w)/d₂ 1.36 1.56 1.53 1.60 1.42 — (9) f₂/f_(w) −2.16−2.18 −2.36 −2.31 −2.17 −2.13 (10)  f₁/f_(w) 6.67 6.85 7.25 8.06 7.758.27 (11)  M₁/M₃ 0.55 0.59 0.59 0.62 0.63 0.59 (12)  M₁/I 1.82 1.94 2.261.56 1.96 1.91 (13)  f₄/f_(w) 2.61 3.80 2.95 2.66 2.97 3.21 (14) β_(T4)/β_(W4) 1.36 1.50 1.76 1.47 1.44 1.42 (15)  f₃/f₄ 1.37 0.99 1.311.31 1.12 1.02 (16)  f₁/f₂ −3.08 −3.15 −3.08 −3.48 −3.57 −3.88

The zoom lens system according to the present invention is applicable toa digital input device such as a digital still camera, a digital videocamera, a mobile telephone, a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera or avehicle-mounted camera. In particular, the present zoom lens system issuitable for a camera such as a digital still camera or a digital videocamera requiring high image quality.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

1. A zoom lens system comprising: at least three lens units eachcomposed of at least one lens element, wherein an interval between atleast any two lens units among the lens units is changed so that anoptical image of an object is formed with a continuously variablemagnification, the zoom lens system, in order from the object side tothe image side, comprises: a first lens unit having positive opticalpower; a second lens unit that includes a lens element having areflecting surface for bending a light beam from an object and that hasnegative optical power; and subsequent lens units including at least onelens unit having positive optical power, and the following condition (1)is satisfied:1.50<M ₁ /f _(W)<3.00   (1) (where, Z=f_(T)/f_(W)>3.90) in which, M₁ isan amount of optical axial movement of the first lens unit at the timeof zooming from a wide-angle limit to a telephoto limit, f_(W) is afocal length of the entire zoom lens system at a wide-angle limit, andf_(T) is a focal length of the entire zoom lens system at a telephotolimit.
 2. The zoom lens system as claimed in claim 1, wherein any one ofthe lens units, any one of the lens elements, or alternatively aplurality of adjacent lens elements that constitute on lens unit move ina direction perpendicular to an optical axis.
 3. The zoom lens system asclaimed in claim 1, wherein the reflecting surface bends byapproximately 90° an axial principal ray from the object.
 4. The zoomlens system as claimed in claim 1, wherein the lens element having areflecting surface is a prism.
 5. The zoom lens system as claimed inclaim 4, wherein the prism has negative optical power.
 6. The zoom lenssystem as claimed in claim 1, wherein the lens element having areflecting surface is a mirror.
 7. The zoom lens system as claimed inclaim 1, wherein the subsequent lens units, in order from the objectside to the image side, comprise a third lens unit having positiveoptical power and a fourth lens unit having positive optical power, andwherein the following condition (2) is satisfied:3.20<f ₃ /f _(W)<4.00   (2) (where, Z=f_(T)/f_(W)>3.90) in which, f₃ isa composite focal length of the third lens unit, f_(W) is the focallength of the entire zoom lens system at the wide-angle limit, and f_(T)is the focal length of the entire zoom lens system at the telephotolimit.
 8. The zoom lens system as claimed in claim 1, wherein thesubsequent lens units, in order from the object side to the image side,comprise a third lens unit having positive optical power and a fourthlens unit having positive optical power, and wherein the followingcondition (3) is satisfied:0.40<f ₃ /f _(T)<0.90   (3) (where, Z=f_(T)/f_(W)>3.90) in which, f₃ isthe composite focal length of the third lens unit, f_(W) is the focallength of the entire zoom lens system at the wide-angle limit, and f_(T)is the focal length of the entire zoom lens system at the telephotolimit.
 9. The zoom lens system as claimed in claim 1, wherein thesubsequent lens units, in order from the object side to the image side,comprise a third lens unit having positive optical power and a fourthlens unit having positive optical power, and wherein the followingcondition (4) is satisfied:0.40<D ₃ /f _(W)<1.20   (4) (where, Z=f_(T)/f_(W)>3.90) in which, D₃ isan optical axial thickness of the third lens unit, _(f) _(W) is thefocal length of the entire zoom lens system at the wide-angle limit, andf_(T) is the focal length of the entire zoom lens system at thetelephoto limit.
 10. The zoom lens system as claimed in claim 1, whereinin zooming from the wide-angle limit to the telephoto limit at the timeof imaging, the second lens unit does not move in the optical axisdirection.
 11. The zoom lens system as claimed in claim 2, wherein anyone of the lens units other than the second lens unit, any one of thelens elements other than the lens element having a reflecting surface,or alternatively a plurality of adjacent lens elements that are otherthan the lens element having a reflecting surface and that constituteone lens unit move in a direction perpendicular to the optical axis. 12.The zoom lens system as claimed in claim 11, wherein a third lens unitlocated on the most object side among the subsequent lens units moves ina direction perpendicular to the optical axis, and wherein the followingcondition (5) is satisfied:0.10<f _(W) /Y _(W)×10⁻³<0.20   (5) (where, Z=f_(T)/f_(W)>3.90) inwhich, Y_(W) is an amount of movement of the third lens unit at the timeof maximum blur compensation in a focal length f_(W) of the entire zoomlens system at the wide-angle limit, f_(W) is the focal length of theentire zoom lens system at the wide-angle limit, and f_(T) is the focallength of the entire zoom lens system at the telephoto limit.
 13. Thezoom lens system as claimed in claim 11, wherein a third lens unitlocated on the most object side among the subsequent lens units moves ina direction perpendicular to the optical axis, and wherein the followingcondition (6) is satisfied:0.20<f _(T) /Y _(T)×10⁻³<0.35   (6) (where, Z=f_(T)/f_(W)>3.90) inwhich, Y_(T) is an amount of movement of the third lens unit at the timeof maximum blur compensation in a focal length f_(T) of the entire zoomlens system at the telephoto limit, f_(W) is the focal length of theentire zoom lens system at the wide-angle limit, and f_(T) is the focallength of the entire zoom lens system at the telephoto limit.
 14. A lensbarrel for holding an imaging optical system that forms an optical imageof an object, wherein the imaging optical system is the zoom lens systemas claimed in claim 1, and wherein in an imaging state, the first lensunit is held in a manner movable in a direction of the light beam fromthe object, and in an accommodated state, the lens element having areflecting surface escapes to an escape position different from aposition located in the imaging state.
 15. The lens barrel as claimed inclaim 14, wherein in the accommodated state, the second lens unitescapes to an escape position different from a position located in theimaging state.
 16. The lens barrel as claimed in claim 15, wherein thesecond lens unit escapes in the optical axis direction toward the imageside of the imaging optical system.
 17. The lens barrel as claimed inclaim 16, wherein the imaging optical system satisfies the followingcondition (7):0.50<ΣD ₁₂ /Σd _(AIR)<1.00   (7) in which, ΣD12 is an optical axialtotal thickness of the first lens unit and the second lens unit, andΣd_(AIR) is an optical axial total air space between the respective lensunits that are located on the image side relative to the second lensunit and that move in the optical axis direction in zooming.
 18. Animaging device capable of outputting an optical image of an object as anelectric image signal, comprising: an imaging optical system that formsthe optical image of the object; and an image sensor that converts theoptical image formed by the imaging optical system into the electricimage signal, wherein the imaging optical system is the zoom lens systemas claimed in claim
 1. 19. A camera for converting an optical image ofan object into an electric image signal and then performing at least oneof displaying and storing of the converted image signal, comprising: animaging device including an imaging optical system that forms theoptical image of the object and an image sensor that converts theoptical image formed by the imaging optical system into the electricimage signal, wherein the imaging optical system is the zoom lens systemas claimed in claim 1.